Hydraulic method of mining and conveying coal in substantially vertical seams

ABSTRACT

Coal can be mined from a substantially vertical or steeply inclined seam by forming a cavity in the seam and filling the cavity with a magnetite slurry having a specific gravity greater than the coal being mined therefrom. As the coal is dislodged, it will float to the top and be pumped from the cavity by the excess magnetite slurry being supplied to the cavity. A coal-magnetite slurry separator is used to separate the coal from the magnetite slurry, whereupon the magnetite slurry is reinjected into the cavity.

United States Patent 11 1 Poundstone et a1. Apr. 1, 1975 1 1 HYDRAULICMETHOD OF MINING AND 2.276.075 3/1942 Wuensch 252/85 s CO V NG COAL INSUBSTANTIALLY 2,944,019 7/1960 Thompson et a1. 252/85 B 3.637.263 1/1972Wasp... 302/14 VERTICAL SEAMS 3.719.397 3/1973 Wasp 302/14 [75]Inventors: William N, Poundstone, Pittsburgh, 3.776.594 12/1973 Haspert299/18 Pa.; William J. Miller, Ponca City.

Okla. Primary Examiner-Ernest R. Purser [73] Assignee: Continental OilCompany, Ponca City. Okla. 1 1 ABSTRACT [22] Filed: Aug. 29. [973 Coalcan be mined from a substantiallyyertical or steeply inclined seam byforming a cavity in the seam [21] Applv No: 392.576 and filling thecavity with a magnetite slurry having a specific gravity greater thanthe coal being mined 152 US. Cl 299/17, 299/18, 302/14 1511 lm. c1. EZlc37/06 AS the coal is dislodged It will fleet lo the p and he [58] Fieldof Search 299/17, 18; 175/66, 263, P p from the Cavity y the eXeeSSmagnetite Slurry 175/20 302 14 252 35 3 being supplied to the cavity. Acoal-magnetite slurry separator is used to separate the coal from the[56] Ref Ci d magnetite slurry, whereupon the magnetite slurry isreinjected in) the Cavity.

1.2115347 11/1918 01m 175/263 x 4 C a 6 Drawing g r 41 37 2a 1 g a l lall so I MAGNITITE 25 a i SLURRY com. SEPARATOR O D O 1 o b k I) l 6 07-20 I g 1 18 \f .t 9 4, mfg; 'ts'e'z gww? -oc) P'DP Bfl myyn *a Q 48 o0 0 8.7798 ti po /7 9 80 ';a fl D 00 .2

TENTH] APR 1 i8?5 SHEET 1 OF 3 COAL SEPARATOR FIG. I

oo//////// 00 /L L/l/// HYDRAULIC METHOD OF MINING AND CONVEYING COAL INSUIISTANTIALLY VERTICAL SEAMS DISCUSSION OF THE PRIOR ART Vertical seamshave generally been mined in the past by use of strip mining; however,strip mining can only be economically performed for fairly shallowpenetrations into the coal seam. since a vast amount of debris and rockmust be removed in order to reach any depth in the coal seam. Stripmining is only feasible when the coal scam has a substantial width andfairly high grade.

A forming of mining known as cut-and-fill stopping is also used forsubstantially vertical seams and is accomplished by digging a tunnelalong the seam forming ore chutes above the tunnel and mining out thecoal, dropping it into the ore chutes and thence into the carspositioned below said chutes; however. where the seams may he badlyfolded. it may be extremely difficult to mine the seams from underneath.

Another method of mining vertical seams can be used. such as theshrinkage stoppage method. The particular method used will depend on thecompetency of the hanging wall, the particular form of the seam.

BRIEF DESCRIPTION OF THE INVENTION This invention describes a method formining sub stantially vertical seams by forming a cavity in the seam.either from the top or from a desired depth. fill ing the cavity withmagnetite slurry which has a specific gravity greater than the specificgravity of the coal. and then dislodging the coal mechanically whereinthe coal will tloat to the surface and be pumped from the cavity by theexcess magnetite slurry being supplied thereto.

Separators are used to separate the coal which is conveyed from theseparator from the slurry which is pumped back into the cavity alongwith additional magnetite. if needed. to maintain specific gravity abovethat of the coal. In one embodiment the cavity is formed from thesurface and is acceptable for high grade coal where the amount ofimpurities in the coal is minor compared to the tonnage of coal mined.Under ordinary conditions. however. debris and unusable materials canamount to as much as percent of the coal mined. The preferred embodimentovercomes the accumulation of debris by drilling a bore hole to adesired depth in the coal seam. anchoring a magnetite recovery pipe atthe bottom of the bore hole. and mounting a mechanical dislodgingapparatus around the magnetite recovery pipe. Magnetite slurry is pumpeddown the dislodging device and against the mine surface. Mechanicaldevices. such as picks. will dislodge the coal which is flushed away bythe magnetite being jetted against the coal surface. As the coal isdislodged. the apparatus is pulled up in the manner of raise drilling.The dislodged coal floats to the surface because of its lower specificgravity and is conveyed through a pipe or trench to a magnetiteslurry-coal separator. When the cavity reaches the surface of the earth,the dislodging apparatus is removed. Fresh water is pumped into thecavity. and the magnetite slurry is removed by back-flushing the freshwater through the debris and into the magnetite recot cry pipe where itis pumped from the cavity.

In the above manner most of the magnetite can be recovered from thecavity. The magnetite slurry being recovered will be applied to amagnetite-water separator. The water will be returned to the minecavity, and the recovered magnetite will be applied to the new ca\itybeing mined.

BRIEF DESCRIPTION OF THE FIGURES FIG. 1 is a cross-sectional view of acavity being formed using the raise drilling principle;

FIG. la is an alternate embodiment of the dislodging arm shown in FIG.I;

FIG. 2 is a cross-sectional view of a mined cavity illustrating themagnetite recovery process;

FIG. 3 is atop view of a mining operation illustrating the process ofrecovering the magnetite from a mined cavity, mining a new cavity, andsupplying the recow ercd magnetite to the cavity being mined; and

FIGS. 4 and 5 illustrate the method of mining a substantially verticalseam by forming the cavity from the surface of the earth.

Referring to FIGS. I through 3. the preferred em bodiment isillustrated.

A bore hole III is formed in the seam to a desired depth which may. forexample. be from 7()() to 900 feet in depth. A magnetite recovery pipe11 (to be later described) is insertcd axially into the bore hole. Ananchoring means 12 is attached to the bottom of magnetite recovery pipeI I and comprises a ring 13 and a plurality of extending rods 14. Aplurality of openings 15 perforates the lower end of recovery pipe II.These openings may be slots or circular in shape and may be plugged toprevent entry of debris, by any means such as wax or plastic which canbe removed at a later time. The type of slots used and the pluggingmaterial. if used. are well known in the art and will not be furtherdescribed herein.

A dislodging pipe 15 is slipped axially over recovery pipe II and has arotatable seal 16 at its lower end. Dislodging pipe 15 may be formedfrom a plurality of sections "joined at 18 by a threaded joint. It ispreferable that the outer circumference of the pipe be completelyuniform across the joint.

Bore hole I0 has a surface seal formed by a pipe 20 forced into orcemented into bore hole I0. Pipe 20 terminates in a pipe end 2]. boltedby means of a flange 24 to surface seal pipe 20. Pipe end 2! has a seal25 which provides a fluid tight seal for dislodging pipe l5 and yetpermits rotation of pipe I5. Pipe end 21 also has an outlet 22 which isconnected through a pipe 23 to a magnetite slurry-coal separator 25. Themagnetite slurry-coal separator basically incorporates a conveyer whichremoves the coal floating on the surface of the magnetite and depositsthe coal in a dump or other location and returns the magnetite to themine cavity. Such magnetite slurry-coal separators are described on page9-26 through page 9-35 in a book entitled Coal Preparation. ThirdEdition. by Joseph W. Leonard and David R. Mitchell and publishedthrough The American Institute of Mining, Metallurgical. and PetroleumEngineers. Inc.. and published by the Port City Press. Inc., Baltimore.Md. The magnetite slurry is re turned through a line 26 to a pump 27 toinjection line 28 to a hydraulic motor 29 and to the inside ofdislodging pipe IS in the direction of arrow 30. As the magnetite slurryis forced through hydraulic motor 29. it causes rotation of a shaft 31which is connected through threads 32 to a pipe section 17 of dislodgingpipe 15. Hydraulic motor 29 is held in place or moved by means of ahoist 35 which contains a book 36 interlocked with an eye 37 which ispermanently attached to the hydraulic motor 29. A plurality oflines 40is connected to a hoist pulley (not shown). The entire structure issupported by a rig 41 which is attached by any suitable means. eitherportable or permanent. to the surface of the earth.

A pipe clamping means is attached through a flange 45 to pipe end 2|. Awedge-type pipe retaining means 46 is mounted onto flange 45. Wedgeretaining means 46 permits upward movement and rotational movement ofdislodging pipe but will prevent pipe [5 from moving downwardly into thecavity.

The upper end 50 of magnetite recovery pipe I 1 contains a small slot 5|which permits entry of magnetite slurry into pipe H but restricts theloss in pressure so that the majority of the pressure is available atthe bot' tom of dislodging pipe 15.

A dislodging arm 60 is attached through a pivot 61 to the bottom end ofdislodging pipe 15. A plurality of jets 62 is mounted on dislodging arm60 and directed upwardly so as to create a high velocity fluid streamagainst the mine surface 63. A flexible pipe 64 communicates fluid fromthe inside ofdislodging pipe 15 to the jets 62. A roller 65 maintains aprecise distance between the jets and mining surface 63. A suitablemechanical lock (not shown) maintains dislodging arm 60 in a rigidposition once the arm has moved to the proper cutting position.

Referring to FIG. In, an alternate embodiment of the dislodging arm isshown and essentially comprises a plurality of picks 70 attached betweenjets 62. In this embodiment the jets principally provide means forremoving the dislodging chips of coal and debris rather than provide ameans for removing the coal by high velocity of fluid.

MINING OPERATlON The operation ofthe preferred embodiment is as follows:

The dislodging pipe [5 and dislodging arm 60 are lowered into bore holewith the dislodging arm in the position shown by dotted lines 71. Themechanical locks maintaining dislodging arm in the position shown bydots 7! can be released by any well known method such as a mechanicalpin. an electrical squib. or other well known triggering devices. Oncethe dislodging arm 60 is released. pump 27 initiates the pumping ofmagnetite slurry into hydraulic motor 29, down the inside of pipe in thedirection of arrow through flexible tube 64 to jets 62. Hydraulic motor29 will begin rotating as soon as the flow through the motor becomessufficient to generate enough horsepower to operate the hydraulic motor.As motor 29 begins to rotate, dislodg ing pipe 15 begins to rotate.causing dislodging arm 60 to rotate about the wall ofthe bore hole. Thehigh pressure from the jets 62 begins eroding the bore hole wall fromcavity 90. The jet fluids will also commence filling up cavity 90 andthe bore hole ill with fluid or magne tite slurry. Once the bore hole isfilled. slurry will flow down through outlet 22. down pipe 23, tomagnetite slurry, and coal separator 25 for recirculation through pipe36 to pump 37. The coal 9]. for example. will be dislodged and proceedsto the surface, since it has a specific gravity less than that of themagnetite slurry.

Debris 92. for example. will fall to the bottom of the well bore andcavity 90. Roller will maintain the distance between the mining surface63 and jets 62; or. if picks are used, the picks (see FIG. la) willmaintain contact with mining surfaces 63 eroding the mining surface.

Seal 16 permits rotation of dislodging pipe 15 with respect to magnetiterecovery pipe 1] and yet retains the fluid pressure inside pipe l5.Anchor l2 retains magnetite recovery pipe down-hole and in positionduring the rotation and lifting ofdislodging pipe 15. Metal rods 14 arespring biased away from the outside wall of pipe I1 and have sufficientdiameter to engage the bore hole wall. Thus. if pipe I] rises, rods l4will dig into bore hole wall ll, retaining the pipe into position.

The particular anchor disclosed here should properly hold the recoverypipe II in position; however. other types of anchors could be used, forexample. an inflatable packer. auger. and other well known apparatus forsecuring a pipe in a particular location. It is preferable. of course.that the particular anchor used be releasable at a later time so thatthe pipe can be recovered after the recovery operation is complete.

As dislodging arm 60 rotates the coal will soon be eroded to the pointwhere either the picks or jets can no longer remove any coal. At thispoint hoist 2S and its associated equipment will raise the hydraulicmotor 29 through book 36 and eye 37. lifting pipe l5. Since dislodgingarm 60 is connected to pipe 15 it will likewise rise with the pipe,thereby permitting dislodging arm to re-engage the mining surface 63. Asa section of pipe I7 is raised to the point where a joint [8 is abovewedge clamp 46. the hoist 35 will be lowered. wedging the pipe of theclamp 46. Hydraulic motor 29 will then be reversed or mechanicallyunscrewed from pipe 17 and that section of pipe removed. Motor 29 willthen be connected with the next lower section 17 of pipe 15. Theprocedure will be followed until the dislodging arm 60 has been cut awaymining surface 63 in a nearly cylindrical form to a depth near thesurface of the ground which will under normal conditions be the bottomof surface seal 20. At this time pipe end 2|, including wedge clamp 46.will be removed along with hydraulic motor 29. and the magnetiterecovery process will commence.

MAGNETITE RECOVERY Referring to FIGS. 2 and 3. but in particular to FIG.2, a completely formed cavity is illustrated having magnetite recoverypipe I] therein anchored at the bottom by anchor means I2. Pipe end 2lhas an extension pipe passing therethrough and connected to the end 50of pipe II. The short portion containing slot 51 has been removed. Pipes96 are connected from exten sion 95 to the inlet of pump 27. A magnetitewater separator It)" has its inlet l0l connected through pipe I02 to theoutlet [03 of pump 27. The reclaimed magnetite is recovered throughoutlet I04 and the water is recovered through outlet I05. Water fromoutlet is connected through a line I06 to a second pump I07 to the waterinlet I08 of pipe end 2].

OPERATlON The importance of recovering magnetite in the cavity anddebris cannot be minimized. It is estimated that in a cavity ofapproximately 700 feet in height and a radius of three feet,approximately l.tl(ltl tons of mined material can be recovered. Assuming20 percent of the material is debris and 80 percent ofthe material iscoal. approximately Kilt) tons of coal will be recovered and 200 tons ofdebris will lie in the bottom of the cavity. Assuming the debris willnot be firmly compacted. it will fill from A to ls of the cavityMagnetitc has a specific gravity of 5.0. Assuming a good grade ofmagnetite. approximately 90 percent of the magnetite will be liner thansixe 360. A certain portion of the magnetite will settle to the bottomofthe cavity during the mining process particularly since the magnetiteis in the form of a slurry and not in the form of a solution. If, forexample. l()() tons of magnetite settled with the debris to the bottomof the cavity, over $2.000 worth of magnetite would he lost if no methodof recovery were possible. In order to recover the magnetite. thereforimproving the economics of this form of mining. fresh water is pumpedthrough pump I07 to inlet I08 into the cavity 90. The fresh water willcause back-flooding of the debris: and. since magnetite is the heaviestmaterial in the cavity. it will settle to the bottom near the openingsof pipe I]. Pump 27 will then suck up the fresh water and magnetitethrough holes I5 up pipe I I in the direction of arrow 1 I5 and throughpipe 96 to pump 27 where it is moved through pipes I02 and II tomagnetite water separator I00. Magnetite water separators are well knownin the art. Such devices are clearly described in the hook CoalPreparation," (supra). The reclaimed magnetite is saved for futuremining operations. and the water is returned through lines I06 to pump107 [if needed) and thence to cavity 90. Once the amount of magnetitebeing recovered is insufficient for the energy being expended to recoverit. the magnetite recovery process is discontinued. Pipe 96 is removedalong with pipe end 2I. Pipe section 95 is connected to hoist 35. andthe entire pipe II lifted out of the cavity 90. Anchor I2 will disengageby either tearing away the walls of the bore hole portion remaining or.rods I4 will bend or break off as pipe is pulled tip through the debris.

The above system has certain advantages. For example. it does permit ameans of recovering a high cost item such as the magnetite used inmining the ore; and it does permit recovery of the magnetite recoverypipe. Since the pipe was put in initially. no hole need be drilled at alater time through unconsolidated debris which would pose a difficultdrilling problem under the best of conditions.

MINING SYSTEM Referring to FIG. 3 the entire mining system is disclosedshowing the process for mining a narrow vertical seam. A mined outcavity I is followed by a mined out cavity I2I \vhere magnetite recoveryis in process and a partially mined out cavity 122 where mining is stillin progress. In the recovery cavity IZI. pipe 96 is applying waterthrough pipe end 2I to cavity IZI. and pipe I08 is pumping out themagnetite slurry through pump 27 to magnetite water separator I00. Thewater is being returned through line I06 to pipe 96 and back to cavityIZI. Additionally water. if needed. is added through line 123. Themining section has the magnetite slurry being applied through line 28into pipe end 21 and the magnetite slurry and coal being recoveredthrough pipe 23 to magnetite slurry and coal separator 25. The magnetiteonce separated is applied through line 26 to a slurry mixer I24 wherewater I25 and magnetitc I26 are being added by amounts to insure theproper specific gravity of the magnetite. Once the slurry mixture isproper. it is returned through line 28 to the cavity 122. Magnetitcbeing recovered from separator 100 is transferred by conveyer or lineI30 to the slurry mixer 124.

The separator I00. the slurry-coal separator I25. the slurry mixer I24.pump 27 and any other necessary pumping and power equipment can bemounted on a single or plurality of vehicles in order to providemobility to the system.

SURFACE CAVITY MINING Referring to FIGS. 4 and 5. a surface cavitymining system is illustrated. A platform 200 has an outer casing 2(IIrotatably attached by a bearing 202 to platform 200. Dislodging pipe I5is mounted inside casing 20I. Pump 27 has an inlet 26 connected to asource ofmagnetitc slurry (not shown). The outlet from pump 27 isconnected through pipe 28 to a rotatable pipe connection 203. A motor204 is connected through a winch 205 to rig 4I. Motor 204 can beelectric or hydraulic of sufficient power to turn dislodging pipe I5 anddislodging arm 60. Jets 62. which. as previously described. can also hepicks such as 70 in FIG. I2. are in engagement with coal seam 206.

OPERATION The operation of the dislodging arm shown in FIGS. 4 and 5 issubstantially identical to the operation of the dislodging arm 60described in FIGS. I through 3. Magnetite slurry 207 fills the cavityand overflows through a trench 208 to a recovery area (not shown). Coal9] floats on the magnetite slurry and can be easily removed. The systemdescribed in FIGS. 4 and 5 is extremely useful for very high grades ofcoal with little debris embedded in it. Obviously. as the debrisaccumulates. the mining must be stopped and the debris mechanieallyremoved before mining can he recommenced.

MAGNETITE SLURRY Coal of a high grade anthracite normally has a specificgravity of from l.4 to L7. The density of the magnetite must be greaterthan the density being mined in order for the coal to float; therefore.if the density of the coal is L4. the density of the magnetite must beat least L5 in order for the magnetite to have adequate buoyancy.Bituminous coal normally ranges from a specific gravity of I .4 to I .5.Debris on the other hand usually has a specific gravity of 2.0;therefore, it is relatively easy to separate the debris from thespecific gravity; however, it is also obvious that the specific gravityof the magnetite must be controlled sufficiently to maintain its densityless than that of the debris but more than that of the coal being mined.Most debris does have a specific gravity of 3.0; therefore. errors inthe adjustment in the specific gravity would still not render the systeminoperable but would merely provide less pure coal.

These and other modifications can be made to the embodiments illustratedand still be within the spirit and scope of the invention as describedin the specification and appended claims.

We claim:

I. The method of producing coal from a seam of coal comprising:

boring at substantially vertical pilot hole into said seam ol coal;

inserting a retracted coal dislodging tool into said bored pilot hole;

extending said dislodging tool;

raise drilling with said extended dislodging tool to form a cylindricalcavity.

injecting under pressure into said bored pilot hole and said formedcavity material having a specific gravity greater than said coal.

removing said dislodged coal and said material through said pilot hole;

separating accumulated amounts of said dislodged coal and material beingremoved from said bored pilot hole;

re-injecting said separated material into said bored pilot hole; and

continuing to raise drill until said dislodging tool is in closeproximity to the surface of said seam of coal.

2. A method as described in claim 1 wherein said method includes:

boring another substantially vertical pilot hole in said' seam of coalin the proximity of said first- Ill mentioned formed cavity;

inserting said retracted coal dislodging tool into said another boredpilot hole.

extending said retracted coal dislodging tool and raise drilling to forma cavity:

injecting water through said t'irstanentioned hore hole and into saidcavity to remove said material therefrom:

separating said material from said injected water; and

inserting said separated material into said another bore hole.

3. A method as defined in claim 2 wherein said material eomprises aslurry formed from magnetite and wa- 4. A method as defined in claim 3wherein said magnetite slurry and water removed from the bottom of saidbore hole is further processed by:

separating said magnetite from said water:

mixing said separated magnetite with water to form a slurry having apredetermined specific gravity: adding said slurry to said another borehole: and

returning said separated water to said bore hole.

=l k l

1. The method of producing coal from a seam of coal comprising: boring asubstantially vertical pilot hole into said seam of coal; inserting aretracted coal dislodging tool into said bored pilot hole; extendingsaid dislodging tool; raise drilling with said extended dislodging toolto form a cylindrical cavity; injecting under pressure into said boredpilot hole and said formed cavity, material having a specific gravitygreater than said coal; removing said dislodged coal and said materialthrough said pilot hole; separating accumulated amounts of saiddislodged coal and material being removed from said bored pilot hole;re-injecting said separated material into said bored pilot hole; andcontinuing to raise drill until said dislodging tool is in closeproximity to the surface of said seam of coal.
 2. A method as describedin claim 1 wherein said method includes: boring another substantiallyvertical pilot hole in said seam of coal in the proximity of saidfirst-mentioned formed cavity; inserting said retracted coal dislodgingtool into said another bored pilot hole; extending said retracted coaldislodging tool and raise drilling to form a cavity; injecting waterthrough said first-mentioned bore hole and into said cavity to removesaid material therefrom; separating said material from said injectedwater; and inserting said separated material into said another borehole.
 3. A method as defined in claim 2 wherein said material comprisesa slurry formed from magnetite and water.
 4. A method as defined inclaim 3 wherein said magnetite slurry and water removed from the bottomof said bore hole is further processed by: separating said magnetitefrom said water; mixing said separated magnetite with water to form aslurry having a predetermined specific gravity; adding said slurry tosaid another bore hole; and returning said separated water to said borehole.